The concept of paranoia has developed virtually simultaneously in Germany and France at the beginning of the nineteenth century. Originally, the idea of a disease of only a part of the soul was in the foreground of discussions. At the era of positivism and the belief of psychiatric illnesses purely as consequences of organic disorders, the concept changed to psychopathologic findings. Now delusions and particularly their systematic character were emphasized. Moreover, the absent impairment of "mental life in its entirety" was given prominence. At the beginning of the twentieth century, the arising concept of schizophrenia thrusts the discussion of paranoia into the background. It was not possible to find out which parts of paranoia were absorbed by dementia praecox. Finally, the development of modern diagnostic manuals revived the old clinical picture mainly because of its clinical evidence and the distinction from schizophrenia.